1. Field of the Invention
The invention relates to an automatic transmission for an automobile, and is particularly applicable to an automatic transmission in which plural clutches are closely positioned. More particularly, the invention relates to the structure of such a clutch section.
2. Related Art
Automatic transmissions for vehicles, such as automobiles having a structure wherein plural clutches are closely (“collectively”) positioned are known. For example, a structure in which three clutches C1, C2 and C3 that operate independently when a vehicle moves forward and that are collectively disposed on the front side of a gear section having a plurality of planetary gear units is disclosed in FIG. 5 and FIG. 7 of Japanese Patent Application Laid-Open No. 4-285347. This structure is capable of providing six forward shift speeds because, as mentioned above, each of the three clutches C1, C2 and C3 is independently operated.
While multi-speed automatic transmissions are in demand in order to improve fuel consumption, greater compactness is also demanded. However, a greater number of speeds and compact size are not compatible in an automatic transmission.
In the above-mentioned related art, in order to independently operate the three clutches C1, C2 and C3, the three clutches C1, C2 and C3 need to be independently structured. However, because it is necessary to combine the positions of the three clutches C1, C2 and C3 to provide an engagement state for each shift speed, it is difficult to have a compact structure. Therefore, even if the six forward shift speeds are achieved, the overall size of the automatic transmission is increased. In other words, it is difficult to achieve a multi-speed transmission in a compact size with the structure shown in the above-mentioned related art.